heat index, the dramatic transformation of Corey Harrison. Losing 200 pounds after visiting his doctor. Abbie Boudreau has the story. Reporter: Pawn stars favorite isn't so big anymore. After a dramatic 190-pound weight loss. Transforming from this to a much leaner look today. How are you feeling? I feel good. It's weird to feel better at 31 than at 25. Reporter: He says a routine visit to the doctor was enough to scare him straight, after finding out he was pre-diabetic. I was freaked about it, and I see the place they do the lap bands, pulled in, I didn't have much money at the time, I pulled out four credit cards, there you go. Reporter: At his heaviest, the history channel reality star weighed more than 400 pounds. I thought I felt Normal. Reporter: It worked, and three years later, he exercises regularly and eats right. I can only have about 4 to 5 ounces of food in the stomach. When you have that space, you don't want to fill it up with crap. Reporter: Feeling and looking better than ever at 210 pounds, fans hardly recognize him anymore. I hear a lot of it looks like him, but I'm not sure. You know, it's the beard, it's the long hair, it's the weight loss. Welcome to the Mecca of transformers. Even his long-time best friend Austin Columbia lee Russell is looking to him for unexpected inspiration. Look at his before and after photos. He thought we were going to be fat guys together, and when I lost the weight, he starts losing weight. He did it all with diet and exercise. Lost almost a hundred pounds. Reporter: Not looking as good as you. Of course not. He's the side kick. Reporter: Abbie Boudreau, ABC news, Las Vegas. Pawn stars airs Thursday nights on history channel. And next, elle Macpherson, she is looking good.

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The Appraiser, the Spotter and Big Hoss

The Harrisons return to the History Channel's 'Pawn Stars' for a second season.